Minimizing Downtime with AWS Database Migration Service (CDC)
A company is migrating a monolithic application to AWS. The application has a relational database with complex queries and requires low-latency read replicas. Which database migration strategy minimizes downtime and supports heterogeneous migrations?
Quick Answer
Migrating a relational database to AWS while minimizing downtime and supporting a heterogeneous target, meaning a different database engine than the source, points specifically at AWS Database Migration Service used with ongoing replication, because DMS is designed to handle exactly that combination: it performs an initial full load of the data and then continuously captures and applies ongoing changes from the source, keeping the target synchronized until the actual cutover happens, which is what allows the switch to the new database to happen with minimal downtime rather than requiring an extended offline export and import window. DMS's support for heterogeneous migrations, moving between different database engines, is what separates it from tools that only work when source and target use the same engine, making it the right fit for a genuinely cross-engine migration. It's useful to distinguish DMS from the other services mentioned here by what each one actually does: AWS Backup handles backup and restore operations, which generally require downtime and isn't built for live, ongoing migration; the AWS Schema Conversion Tool converts database schema and code between engines but doesn't move the data itself, so it's typically used alongside DMS rather than instead of it; and Amazon Redshift Spectrum is a query engine for data already sitting in Amazon S3, unrelated to migrating a live operational database. Whenever a scenario calls for minimal downtime and a migration between different database engines, DMS with ongoing replication is the pattern to expect.
Answer choices
Why each option matters
Answer the question above first, then reveal the full breakdown to understand why each option is right or wrong.
Correct answer & explanation
✓
Use AWS Database Migration Service (DMS) with ongoing replication.
AWS Database Migration Service (DMS) supports heterogeneous migrations (e.g., from Oracle to Amazon Aurora) and can minimize downtime by using ongoing replication to keep the source and target synchronized during the migration. Option A is incorrect because AWS Backup is a backup/restore service, not a live migration tool, and typically requires downtime. Option B is incorrect because AWS Schema Conversion Tool (SCT) is used for schema conversion, not for the actual data migration; it is often used alongside DMS. Option C is incorrect because Amazon Redshift Spectrum is for querying data in Amazon S3, not for database migration.
Answer analysis
Option-by-option breakdown
For each option: why learners choose it and why it is or isn't the right answer here.
- ✗
Use AWS Backup to take a full backup and restore to Amazon RDS.
Why it's wrong here
AWS Backup is a backup service, not a live migration tool.
- ✗
Use AWS Schema Conversion Tool (SCT) to convert the schema and perform a homogeneous migration.
Why it's wrong here
SCT is for schema conversion, not the live migration service.
- ✗
Use Amazon Redshift Spectrum to query the data in place.
Why it's wrong here
Redshift is a data warehouse, not suitable for this use case.
- ✓
Use AWS Database Migration Service (DMS) with ongoing replication.
Why this is correct
DMS supports heterogeneous migrations and minimizes downtime.
Visual reference
Quick reference
AWS S3 Storage Class Comparison
| Storage Class | Min Duration | Retrieval | Use Case |
|---|---|---|---|
| S3 Standard | None | Immediate | Frequently accessed data |
| S3 Standard-IA | 30 days | Immediate | Infrequent access, rapid retrieval |
| S3 One Zone-IA | 30 days | Immediate | Non-critical infrequent data |
| S3 Intelligent-Tiering | None | Immediate–hours | Unknown or changing access patterns |
| S3 Glacier Instant | 90 days | Milliseconds | Archive with instant retrieval |
| S3 Glacier Flexible | 90 days | Minutes–hours | Archive, flexible retrieval |
| S3 Glacier Deep Archive | 180 days | Hours | Long-term compliance archive |
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Same concept, more angles
3 more ways this is tested on PAS-C01
These questions test the same concept from different angles. Work through them to make sure you can recognise it however the exam phrases it.
Variation 1. A company is migrating a custom CRM application to AWS. The application uses a PostgreSQL database. Which migration approach minimizes downtime?
easy- ✓ A.Use AWS Database Migration Service (DMS) with ongoing replication (CDC).
- B.Use AWS Backup to create a snapshot and restore to RDS.
- C.Take a full backup of the source database, restore to RDS for PostgreSQL, and then cut over.
- D.Use pg_dump to export the database and pg_restore to import into RDS.
Why A: AWS Database Migration Service (DMS) with ongoing change data capture (CDC) enables near-zero downtime migration by continuously replicating changes from the source to the target until cutover. Options B, C, and D all require taking the source database offline for backup or export, resulting in significant downtime.
Variation 2. A company is moving their SAP Business One application from an on-premises data center to AWS. The application runs on Windows Server and uses Microsoft SQL Server. They want to use Amazon EC2 for the application and Amazon RDS for SQL Server for the database. They have already used AWS SCT to assess the database schema and found that it is compatible. What should they do next to migrate the database with minimal downtime?
easy- A.Export the database to flat files and upload to S3, then import into RDS
- B.Use AWS SCT to convert the schema and then use AWS DMS
- ✓ C.Use AWS DMS to perform a full load and then enable ongoing replication
- D.Take a full backup of the on-premises SQL Server, upload it to Amazon S3, and restore to RDS
Why C: AWS DMS can perform a full load and then enable ongoing replication to minimize downtime during migration. Option A is wrong because manual export/import requires downtime. Option B is wrong because the schema is already compatible, so using SCT first is unnecessary; DMS can be used directly. Option D is wrong because copying a backup to S3 and restoring to RDS requires downtime during the restore.
Variation 3. A company is migrating a legacy on-premises application to AWS. The application uses a MySQL database with a complex stored procedure that runs every hour and takes approximately 10 minutes to complete. The company wants to minimize downtime during migration. Which TWO approaches should the company use to migrate the database?
medium- A.Use AWS DMS with a full load only, without ongoing replication, and schedule a cutover window.
- ✓ B.Use AWS Database Migration Service (DMS) with ongoing replication from the source MySQL database to an Amazon RDS for MySQL instance.
- ✓ C.Set up an Amazon Aurora MySQL DB cluster and use AWS DMS with the on-premises MySQL database as the source and the Aurora cluster as the target, enabling ongoing replication.
- D.Take a full database dump using mysqldump and import it into an Amazon RDS for MySQL instance during a planned maintenance window.
- E.Create an Amazon RDS for MySQL read replica from the on-premises database.
Why B: AWS DMS with ongoing replication allows continuous synchronization from the source MySQL database to Amazon RDS for MySQL, minimizing downtime during migration. The complex stored procedure that runs hourly and takes 10 minutes is handled seamlessly as DMS captures ongoing changes, enabling a controlled cutover with minimal disruption.
JA
Written by Johnson Ajibi, MSc IT Security
Senior Network & Security Engineer · founder of Courseiva
This PAS-C01 practice question is part of Courseiva's free Amazon Web Services certification practice question bank. Courseiva provides original exam-style practice questions with explanations, topic-based practice, mock exams, readiness tracking, and study analytics to help learners prepare for the PAS-C01 exam.